Economics of Balancing
TA Hydronic College
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Map of U.S. energy need
2
HVAC objectives
All HVAC installations should reach 2 fundamental objectives:
1. To deliver the specified comfort level
2. To reach the first objective, while using a minimum quantity
of energy
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Production
Distribution
Terminal units
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Hydronic control
In theory, current technology involving state-of-the-art
BMS systems makes it possible to achieve these 2 objectives
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In practice, even the most sophisticated control systems lead
often to reduced comfort at increased operation costs
In many cases, problems and therefore
solutions are to be found on the hydronic side
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Symptoms related to typical hydronic problems
 Too hot in some parts, too cold in other parts
 Start-up after a set-back is difficult in some rooms
 Installed power is not deliverable
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 Room temperatures fluctuate
 Higher energy consumption
than expected
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TA Hydronic’s 3 Key Conditions
for
Perfect Hydronic Control
Why and how to satisfy them in the simplest way
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Overflows and underflows
62°F
Without hydronic balancing, the first circuits are in overflow
creating underflows in other circuits.
Control valves cannot solve this problem.
Underflow
= too cold
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74°F
Low
differential
pressure
Overflow
= too warm
High
differential
pressure
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Overflows and underflows
To avoid complaints from building tenants
62°F
1st action:
Pumps are pushed to the maximum
 overflows increase
 underflows are reduced:
But
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74°F
q ~ p
(turbulent flow)
To compensate an underflow of 20%
in a circuit (raising the flow by 25% from 0.80 qc to qc)
The local available Dp must be
increased by 56% !
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Unbalanced plant usually means too high total flow
20% underflow
Dp circuit x 1.56
Increasing Dp circuit by 56%
Requires a brute-force increase
of the pump head H by 56%
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H x 1.56
Leading to a total flow increase
of 25%
qtot x 1.25
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Pumping costs
Increasing the pump head to reduce underflows is very energy consuming.
x 1.95
x 1.56
x 1.25
Pump head Flow
Pumpingcosts  C0 
Pump efficiency
With pumping costs representing up to:
(in annual energy consumption)
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Heating
Cooling
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Overflows and underflows
To avoid complaints from building tenants
2nd action:
Supply water temperature is: increased in heating
(decreased in cooling)
 unfavoured rooms start to be comfortable
 tenants from favoured rooms will react
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Energy waste !
Increased CO2 emission !
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The cost of discomfort
Heating
The cost of 1°F too high
room temperature over a year
4 to 7% *
Cooling
The cost of 1°F too low
room temperature over a year
6 to 10% *
(*) of the plant annual energy consumption
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Material life-time
Overflows means that water velocity is higher than expected per design
v
1273 q
with q in l/s, di in mm
2
di
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Too high water velocity leads to erosion in
pipe elbows and heat exhangers.
Control valves of circuits in overflows work
with very short open/close cycles.
This limits dramatically their actuator life-time.
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Maintenance technician intervention
In unbalanced buildings, tenants claim for bad
comfort conditions.
Maintenance technicians waste their time
repetitively visiting these buildings trying to fight
symptoms.
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Unbalanced
building
Number of
technician
interventions
in an
apartment
building
Balancing performed
in Sep. 2002
Balanced
building
35
30
Case study Sep. 2004.
25
20
15
10
5
0
2001
2002
2003
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Start-up after set-back
When a plant is unbalanced, the
Underflow
startup time is longer for the last circuits
in underflow. Overflows do not result in
higher power output of the terminal units.
Overflow
When a plant is balanced, start-up is
achieved simultaneously in all circuits.
°F
84
Emission
COOLING
120%
Occupancy point
100%
81
78
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75
80%
UNBALANCED
PLANT
BALANCED
PLANT
60%
40%
20%
72
Excessive
start-up time
Start-up time
Time
0%
0%
50%
100%
150%
200%
Flow
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Control valves not under control
In frequent cases, control valves do not control the flow in
terminal units any longer.
They are set fully open by the control system :
At start-up after a set-back
Because of sudden load variation
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Because of weird set-point at the thermostat
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Room temperature control
Hotel in Paris
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Room temperature control
Dear passengers:
Due to Central Airconditioning, we
are unable to control the Lounge
temperature.
Please bear with us.
Thank you!
Beijing International Airport
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Hydronic condition nr 1
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The design flow must be available
at all terminal units in design
conditions.
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Achieving hydronic condition nr 1
Adjusting the design flows in all terminal units in design conditions
 Design conditions are the "worst" plant operating conditions, under which
maximum flow is required : control valves are all fully open.
 If design flows are adjusted under design conditions, they can be obtained
in all other conditions.
> qc
<qc
>qc
fully
open
partly
fully
open
open
fully
open
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>qc
fully
open
>qc
fully
open
>qc
fully
open
This should be achieved while creating
the absolute minimum amount of
additional pressure drops.
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TA balancing concept
 To enable systematic balancing with optimal in pressure drop result,
hydronic distribution pipings must be decomposed into hydronic modules
=
A.6
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A.5
A.4
A
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TA balancing concept
 To enable systematic balancing with optimal in pressure drop result,
hydronic distribution piping must be decomposed into hydronic modules
=
A.6
A.5
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A.4
A
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Turning direction criterion for splitting into modules
For finding balancing valve locations resulting in
the lowest possible sizes
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20 gpm 20 gpm
5 gpm
5 gpm
5 gpm
At any bifurcation between many and many units
turn in the direction of the main flow
and place a balancing valve on the low flow side.
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Balancing methods for hydronic modules
Proportional method
adapted from air system balancing methodologies
not optimal in pressure drops
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Compensated method (Pr. Robert Petitjean, see CIBSE Code W)
designed for application with balancing valves
optimal in pressure drops
by-product: all excess Dp is concentrated in the main valve
TA Balance method (Pr. Robert Petitjean)
fully computerized: automatic determination of the index valve (on
the worst unit)
optimal in pressure drops
by-product: all excess Dp is concentrated in the main valve
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Order for balancing modules
The structure of hydronic modules can
be seen as a hierarchical tree.
=
A.6
A.5
Before a module can be balanced, the
whole descent of this module must be
balanced.
A.4
A
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4
Balancing order:
2
1
3
25
VSP set-point optimisation
System curves
Pump head
[ft]
Too high H
B
50
150
Optimum H
A. System unbalanced
Total flow higher than needed
Pump power: 17.2 HP (100%)
B. System balanced
Total flow adjusted – Excess Dp in main valve
Pump power: 13.7 HP (80%)
C. System balanced
Main valve re-opened; VSP set-point reduced
Pump power: 9.8 HP (57%)
30
90
20
60
10
30
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Pump head Flow
Pump efficiency
C
40
120
0
A
Pumpingcosts  C0 
0
45
200
90
400
135
600
180
800
225
1000
270
1200
Design over
flow
flow
Flow
[gpm]
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Savings are real
Pfizer pharmaceutical production unit
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Installed cooling capacity of 1535 ton (refrig.) 5.4 MW (3 chillers in cascade)
Total design flow: 3400 gpm = 773 m³/h
Problem: production alarms !
80 balancing valves from ½” to 8”
Audit of plant with TA Select based on a first measurement campaign
(presettings calculated, viscosity corrections checked)
Full balancing performed using TA-Balance on one TA-CBI
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Savings are real
Before
balancing
Industrial plant
1535 ton (refrig.) cooling
3914 gpm
112 ft pump head
After
balancing
3400 gpm (-13%)
90 ft pump head (-20%)
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Pumping power reduction :
52 HP = 39 kW
Savings: 25,300 USD/year
17,200 €/year
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The importance of measuring
"When you can measure what you are speaking about and express it
in numbers you know something about it;
but when you cannot measure it, when you cannot express it in
numbers, your knowledge is of a meager and unsatisfactory kind."
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Lord Kelvin, 1883
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Diagnostic is a key point
Through balancing, many hydronic problems may be detected
Terminal units or exchangers wrongly mounted
Pipe damaged or not connected as expected
Shut-off valves partially shut
Check valves or pumps installed back-to-front
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Balancing exposes these flaws while they can still be cheaply repaired.
Diagnostic is one of the main use
of balancing valves.
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System Check
Measurement/Verification:
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Available head
Filters or valves clogged
Pipe damaged or not
connected as expected
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The Three Keys to Perfect Hydronic Control
The design flow must be available
at all terminal units in design conditions.
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The differential pressure across control valves
must not vary too much.
The water flows must be compatible at system interfaces.
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The Three Keys
Three simple conditions to satisfy
in order to make hydronic systems work
as expected from design
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Production
Distribution
Terminal units
33
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Thank you for your attention !
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